The prior art is replete with conditioning systems for treating grain, ground grain, grain feed constituents and the like. Not the least of the prior art ground grain conditioning systems is the anaerobic pasteurizing conditioning system set forth and shown in U.S. Pat. Nos. 4,731,938 and 4,667,418 assigned to the assignee of the present invention and incorporated herein by reference. These systems are adapted for the anaerobic pasteurizing conditioning of grain and ingredients therefor adapted for livestock grain as well as other material. Such systems utilize the advantages of direct fired steam generation which include selectively saturated as well as super-heated steam and non-condensable gases generated therewith for the treatment of various substances.
Conditioning systems which are particularly adapted for the utilization of such direct fired steam are also available in the prior art as shown in U.S. Pat. No. 4,686,779, also assigned to the assignee of the present invention and incorporated herein by reference. Together these systems afford a considerable advance over earlier prior art systems in the treatment of many material substances, particularly livestock feed.
A common problem in prior art conditioning systems of grain, feed grains, vegetables and the like is the particular application of a system to a desired product. The utilization of soybeans has been addressed in a myriad of applications in prior art publications. Such applications are set forth and shown in U.S. Pat. Nos. 2,774,670; 3,993,796; 4,205,094; 4,371,556; 4,391,839; 4,450,176; and 4,664,905 which teach the treatment of soybeans and soybean meal. These systems do not incorporate the utilization of direct fired steam nor do they incorporate the utilization of homogeneous conditioning systems which permit the efficient utilization of the constituents of direct fired steam and the advantages thereof. Selective control of steam temperature, partial pressures and dew point in conditioning systems have only recently been recognized pursuant to various technical developments. Some of these are clearly manifested in the patents referenced above assigned to the assignee of the present invention and incorporated herein by reference. By properly utilizing these developments in the treatment of substances such as ground soybeans or barley, great advances may be achieved over the prior art. In discussing these advances, certain definitions will be necessary and are set forth below.
"Anaerobic" conditioning of matter, as referred to herein, comprises the broad step of exposing matter to a treatment fluid in an oxygen deficient environment. "Pasteurizing," as referred to herein, comprises the step of partial sterilization of a substance through temperature and exposure that kills or retards the growth of certain objectionable organisms, which includes the steps of anaerobic environmental exposure and/or elevated temperature exposure. Finally, "conditioning," as referred to herein, encompasses both anaerobic conditioning and pasteurization but also includes the step of exposing matter to various physical conditions and chemicals which react therewith. The rate of reaction approximately doubles for each increase in temperature of 10.degree. C. These and other terms as defined herein have a direct bearing on the description of the present invention and the problems of the prior art which it overcomes.
The matter addressed herein although specifically recited as soybeans and barley may also be a composition of animal, mineral and/or vegetable products and it may be conditioned for direct use in feed, as well as for pelletizing, flaking, bagging and similar intermediate steps. More particularly, the matter addressed herein includes beans, cereals, seeds, grains, whole grains, feed grains, grain fractions, ground grain particulates, vegetables, meat, and trees (pulp/paper). Unfortunately, few (if any) prior art systems have addressed the technological intricacies of matter conversion through controlled time, temperature, moisture and pressurizing conditions. Few have addressed the chemical aspects of animal digestion and the effects of aerobic and anaerobic bacteria. It should be recognized that food prepared in an aerobic environment cannot be deposited in an anaerobic animal stomach with the expectation of maximum efficiency in conversion and protein bypass. Many of the same considerations can be included in the processing of cereals, seeds, grains, feed grains, vegetables, meat and raw material such as wood.
Prior art treatment fluids have generally been comprised of steam, gases and/or combinations thereof adapted for heating, cooling, moisturizing or drying and/or combinations thereof. In many instances the treatment fluid simply provides elevated heat to the matter for the high temperature variety of "pasteurizing" and killing certain heat sensitive organisms such as salmonella in feed. Unfortunately, this prior art step can also kill many useful organisms and denature amino acids as well as protein. As stated above, pasteurizing can also be effected by providing an anaerobic environment without the necessity of elevated temperatures. However, prior art systems generally use the treatment fluid heat to also attempt to alter the molecular structure of the matter prior to feeding or further processing. In one aspect, this is helpful in increasing solvation and the lubricity of the matter which is useful in subsequent operations such as compression and extrusion. The elevated "pasteurization" heat from the treatment fluid is therein also a source of energy in lieu of higher electromechanical energies which would otherwise be expended if a subsequent processing operation is required. Moisture generated in the particulate matter or deposited thereon by the treatment fluid then serves as a lubricant. It should be pointed out that the British Thermal Unit (BTU) content of conventional steam heat is generally solely a function of the steam volume due to the fact that external combustion boilers are typically used. One means of transferring heat from steam is through its condensation. These considerations have had widespread implications in the conditioning of matter throughout the prior art. Enthalpy levels are critical and when boiler steam is used the only means for adding enthalpy is with the steam. As discussed below for each temperature rise of 20.degree. F., the free and bound moisture level of the particulate matter rises by about one percent. Many problems can develop from too high a moisture level including plugging of pelletizing dies when grain and such subsequent operations are involved.
The most important objective in conditioning many substances such as soybeans, barley, whole and ground grains should be, of course, the nutritive value of the matter and thus, the rate at which the matter can be converted and absorbed during digestion. For this reason excessively elevated heat and high moisture levels are not always the most appropriate pasteurizing or conditioning elements. These harsh conditions tend to destruct essential amino acids in the feed. "Chemical tempering" of the grain can also soften or break down the harder surface of the grain to facilitate digestion. Moreover, degradative microorganisms can be eliminated. Carbonic acid will attack such grain surfaces and the protein encapsulating the starch therein making the protein and starch more available for digestion. The availability of such chemical substances in elevated temperature processing could thus be seen to be extremely useful because the chemical reaction would be exponentially accelerated with temperature. Consequently, the nutritive value of the grain and its shelf-life further enhanced. Unfortunately, the prior art generally does not address such technological intricacies in grain conditioning.
Examples of the prior art processes and problems set forth above include conditioning systems for cooking and/or the heating and moisturizing of particulate matter, such as grain, mainly prior to pelletizing steps. This is but one illustration, and the prior art is replete with such systems. Many of these processes incorporate horizontal steam conditioning vessels and boiler steam heat exchanges. Usually, the flow volumes and retention times of the particulate matter passage with the boiler steam are considered the most critical operational parameters. Contact is thus made in a random fashion between the particles to be heated and the boiler steam within steam chambers. In the case of commercial grain treatment, steam from boilers is usually vented into the steam vessels through which various types of grain and microingredients are forced to travel. Steam injected into the vessel condenses on the grain therein for heating and moisturizing it to preselected conditions. As stated above, the BTU content of boiler steam is generally solely a function of the steam volume and the only means of transferring heat is through its condensation. Problems have thus arisen in the areas of proper cooking temperature, cooking environment, retention time, oxygen availability, homogeneity in treatment, as well as the steam generation itself. This is also true for the conditioning of particulate matter comprised of animal, mineral and/or vegetable products prior to feeding, bagging, compression, or extrusion processes. Both the immediate food value of the matter and its shelf-life are critical to the overall nutritive value of the product.
The prior art of steam vessels for both organic and inorganic material extends into technological antiquity with steam utilized for heating tobacco leaves, grain, flour, vitamins and animal feed for a multiplicity of purposes. As stated above, grain used as animal feed is often treated with steam to improve its digestibility by the animal as well as to improve its food value prior to feeding or pelletizing. This is particularly true of soybeans.
Soybeans are known to contain around 18 to 20% fat or oil. The oil comprises a high cost item that may be sold separately from the soy bean. The by-product of soybean meal that is left after the removal of oil or fat is still rich in protein. For this reason it may be treated by other methods of conditioning for utilization as animal feed. One problem is that animal feed also needs oil and/or fat for proper animal nutrition. For this reason, oil and fat are reintroduced into the soybean meal for preparation of animal feed. The prior art techniques utilizing this preparation include exposing the oil enriched defatted ground soybean to specific time, temperatures and moisture for proper conditioning. Prior art technique utilizes boiler steam which heats and moisturizes the soybean meal prior to introducing the meal to an extruder. In the extruder, the ground and partially conditioned meal is exposed for a brief period of time to extremely high temperatures and pressure. This is somewhat of an expensive step with several disadvantages. Extruding is not the only manner in which such soybean meal can be prepared for animal feed. It has been an accepted technique however due to the fact that the soybean has been previously conditioned for removing the oil therefrom.
Several methods of processing whole beans are available. However, most of the methods that have been developed for commercial use fall into two basic categories. The first, and by far the most common one, is the extruder-type processing. The second is the dry-heat processing. In the extruder type, either whole beans or soybean flour are forced through die holes in an expander extruder. Heat generated from friction, or supplied by externally applied steam, is used to cook the bean to inactivate undesirable components in the beans. These undesirable components include urease and trysin inhibitors. However, the resulting product is physically undesirable and needs additional grinding. This method of processing is usually accompanied by cell rupture, hence the nutrients are normally considered to be "available." For animal feeds, about 20-30% in weight of other carrier grains may have to be added to the soybeans to make the final product manageable. Depending upon the model of extruder-type processing, some drying may be necessary, especially if the material is to be stored prior to use. The second system basically uses dry heat to toast or roast the whole bean. In this system, the whole bean is usually subjected to gas flame for brief intervals to accomplish the cooking. The process does not disrupt the cells and the beans must be ground before mixing into the diet.
Unfortunately, in most expander-extruder type of processing, the feed still needs pelleting in order to increase cell rupture to attain maximum digestibility and absorbability. This extra step is not cost effective. Moreover, the energy cost to run an extruder-type equipment is high. Also, maintenance of this type of equipment is expensive, because the equipment is prone to break down. The second system, namely, the dry-heat processing, is likewise not ideal. The oil from heated ground beans is usually not as well absorbed by an animal as the oil from heated flakes. Most important of all, the desirable chemical reactions do not proceed efficiently under the dry-heat environment. There is also a likelihood of overdenaturing the amino acids and proteins under a dry-heat condition.
An alternative method of processing whole soybeans is boiling or steam cooking in systems similar to that used for batch-type processings of meat scraps. Such commercial equipment, however, has not been designed specifically for soybeans. Other high-cost cooking techniques, such as microwave and infra-red heating techniques, have also been used with varying results.
The actual mechanism whereby unheated soybean meal causes poor fat absorptions and depression in protein digestibility in young chicks and other animals is unknown. However, there are several plausible theories. One is that the trypsin inhibitors stimulate pancreatic hypertrophy and the synthesis of proteolytic enzymes, thus increasing the requirement for amino acids and the ultimate loss of endogenous nitrogen. Another theory is that the undigested protein in raw soybean meal synthesize bile acids and elevate their rate of fecal excretion, thereby depressing fat absorptions. Still another theory is that raw soybeans contain a protein fraction which becomes digestible only after heating.
In general, the degree of improvement on nutritive value is effected by a combination of heat, duration of heating, pressure, and moisture conditions. It has been observed that maximum nutritive value of soybean protein is achieved by treatment with live steam about thirty minutes or by autoclaving at 15 lbs pressure for fifteen to twenty minutes. The improvement in protein efficiency effected by atmospheric steaming at a level of nineteen percent moisture is somewhat higher than at a level of five percent. It is thus clear that the improvement in the nutritive value of soybean protein is related to the destruction of urease, trypsin inhibitors and other biologically active components. And the destruction of the undesirable components is facilitated by a combination effect of heat, moisture, pressure and time.
It has also been documented that excessive amounts of heat may adversely affect the nutritive value of the protein as well as denaturizing amino acids. The damage inflicted by denaturization can usually be overcome by supplementation with lysine and other sulfur-containing amino acids. A reduction of available lysine in overheated commercial soybean meals causes a reduction in efficiency of gains per gram of protein consumed. These deficiencies in overheated soybean meal can be explained by the vulnerability of cystine and lysine to destruction and/or inactivation by heat. Cystine is particularly sensitive to heat. Likewise, lysine not only undergoes destruction when soybean protein is overheated, but much of the lysine is also rendered unavailable. The reason that lysine becomes unavailable is that the amino groups of lysine interact with the reducing groups of sugars. Thus, when soybeans are overheated, the hydrolysis of sucrose may give rise to appreciable levels of reducing sugars which will interact with lysine. Consequently, the peptide bond containing the modified lysine is not susceptible to tryptic cleavage and, hence, no longer physiologically available. The effect is the reduction of the digestibility of soybean protein by pancreatic enzyme. A direct consequence of impaired digestion is the retardation in the rate at which all amino acids are released from the protein during digestion. Since methionine is the limiting amino acid of soybean protein, a delay in digestion leading to an excretion of methionine would only accentuate a deficiency in this amino acid. In addition, a number of other amino acids, including arginine, tryptophan, histidine, and serine are either partially destroyed or inactivated by the excessive heating of soybean meal. Fortunately, some of these amino acids are not limiting in soybean protein, therefore, their partial loss probably does not affect the nutritive properties of the protein.
It is thus clear that new methods and techniques are needed to optimize the conditions under which soybean meal should be cooked to inactive the inhibitors and other undesirable components while at the same time avoid the destruction of critical amino acids. The extent of heating, the duration of heating, the amount of water moisture, pressure and particle size in the processing system must be optimized in relation to one another to obtain maximum nutritive value of soybeans.
It is well known in the prior art to use steam to heat and/or moisturize particulate matter prior to feeding, bagging, flaking or pelletizing. This is particularly true of ground grains and soybeans as described above. As stated, conventional steam conditioning system raises the moisture level and temperature of the mixture which is generally non-homogeneous. Generally, conditioning requires that the particulate matter such as the ground soybeans be mixed with various types of the additives or the oil. Processing full fat soybeans does not require additives, while processing homogeneous conditioning does. Conditioning systems which are capable of providing homogeneous interaction of the ground soy-bean mixture and conditioning steam are relatively new and comprise the subject matter of several of the aforesaid patents assigned to the assignee of the present invention. With these systems and with a properly controlled network, direct fired steam can be utilized to overcome the problems of the prior art.
An important class of naturally occurring substances are carbohydrates. They are found universally distributed among plants, animals, and microorganisms. Carbohydrates are divided into three basic categories: monosaccharides, oligosaccharides and polysaccharides. The monosaccharides usually have three to nine carbon atoms and only one aldehyde or ketone function. The oligosaccharides are oligomers of monosaccharides linked together by glycosidic, or acetal, bonds. Generally, these oligosaccharides contain two to ten monomeric units. The polysaccharides are molecules of great size and are characterized by high degrees of polymerization. Included among polysaccharides are such important substances as glycogen, dextrins, cellulose, and starch. They may be considered as condensation polymers in which the monosaccharides, or their derivatives, are joined together by glycosidic bonds. Because the monosaccharide units of polysaccharides are joined by glycosidic, or acetal, linkages, the polysaccharides are readily hydrolyzed by mineral acids but are resistant to alkaline hydrolysis.
Polysaccharides may be divided into two principal functional groups. The first, which include cellulose, serves principally architectural purposes. The second, which includes glycogen, functions as nutrients. In terms of gross structural features, polysaccharides may also be divided into two groups: homopolysaccharides and heteropolysaccharides. The former is characterized by the repeated occurrence of only one sort of monosaccharides within the molecule, and the latter by the occurrence of two or more types of monomeric units.
One other term for the polysaccharides is the "glycans." It has been suggested that polysaccharides such as starches, glycogen and cellulose, all of which are made up of a single kind of monosaccharide, be called "homoglycans." Those that are made up of two or more kinds of monosaccharides, or their derivatives, are named "heteroglycans." Hence, glucose polysaccharides are sometimes called "glucans," while fructose polysaccharides are "fructans." Polysaccharides made up of mannase and xylose are called "mannans" and "xylans," respectively.
The most abundant structural polysaccharides of plants is cellulose. In fact, it is the most abundant organic substance on earth. Cellulose molecules exist in the cell walls of many plants, not as individual molecules, but in the form of microfibrils that are several angstroms long. These are formed from numerous cellulose chains arranged parallel to one another. The second most abundant organic substance on earth is chitin. It, too, is a polysaccharide that is closely related structurally to cellulose. It performs similar functions, as cellulose, in the lower forms of plant life, particularly the fungi, and in invertebrates, particularly the arthropods. In many species, neither cellulose nor chitin is employed for purposes of cell wall construction and for related architectural functions. Their place is taken by a variety of alternative polysaccharides, including glucans, mannans and xylans.
The cell walls of plants form the skeleton of plants and must be competent to withstand tremendous physical weights. Moreover, plants may experience extremes of environment in terms of osmotic pressure. Finally, the cell wall is the central means of protection against invasion by pathogens.
Cellulose, in the form of microfibrils, accounts for about 20 percent of the weight of the primary cell wall of plants. The remainder is largely composed of other polysaccharides. A little of protein is also present in the cell wall of plants. This protein component contains numerous enzymes. The noncellulose polysaccharides of the primary cell wall are not structured, rather they form an amorphous gel within the interstices of the cellulose matrix. Conversion of primary cell walls into secondary cell walls is accompanied by increased thickness of the wall resulting from additional deposition of cellulose, lignin and others. It is this secondary cell wall which accounts for the ability of plants to withstand substantial physical pressures.
In the preparation of animal feeds from plants, the primary objective is, of course, to increase the nutritional value of the feeds. This objective is accomplished by, firstly, preserving the nutrients in the plants and, secondly, by making the nutrients available, digestible and absorbable by animals. Among the desirable nutrients are starch, peptides, certain amino acids, protein, and oil. Undersirable enzymes and bacteria must be eliminated in the process of preparation lest they interfere with the digestibility and absorbability of the plant nutrients. As discussed above, among the undesirable enzymes are trypsin inhibitors and urease.
Certain grains, such as barley and oats, although high in potential nutritional values for certain ruminant animals, are, nevertheless, not readily digestible by mono-gastric animals such as chicken and pigs. It has been observed that when these mono-gastric animals, such as chicken, are fed with barley, the animals produce profuse and wet excreta. The growth rate of the animals is hence retarded as compared to those fed with corn or wheat.
One reason for the problem with barley as animal feeds is that, in addition to the protein encapsulation of the starch, the outer part of the endosperm also contains water soluble carbohydrate components, mixed linked 1,3:1,4-beta-glucans ("beta-glucans"). While ruminant animals can digest these beta-glucans, the mono-gastric animals cannot. One possible reason is that the stomach of a ruminant animal has certain microflora that can ferment and digest the water soluble beta-glucans. Accordingly, barley, although high in potential nutritional value, is a poor feed for mono-gastric animals.
Various treatment methods have been used to improve the feed value of barley for poultry. Soaking barley in water appears to activate endogenous beta-glucanases in the barley grains. The enzymes beta-glucanases in turn hydrolyze the beta-glucans. An alternate treatment method is to add beta-glucanase isolated from bacterial or fungal sources to the barley diet. Both methods will enhance the nutritional value of the barley in that the growth rate and feed efficiency of barley are increased. In addition, both treatment methods reduced excreta wetness, volume and weight. Moreover, the digestibility of fat, protein and starch of barley diets was improved by these treatments. Unfortunately, soaking of barley will shorten the shelf half-life of the barley. Also, the beta-glucanases obtained from bacterial or fungal sources are expensive. Hence, both treatment methods are impractical for commercial feeds.
It would be a distinct advantage, therefore, to provide a complete system overcoming all these problems of the prior art by utilizing conditioning systems and direct fired steam generation in an effective and reliable manner. The system of the present invention affords such an operation by utilizing the steam and products of combustion of a direct fired vapor generator in conjunction with a pressurized counterflow conditioning vessel having discharge means disposed therein for uniformly passing particulate matter therethrough. The amount of heat for pasteurizing and/or moisture supplied to the matter may be controlled by the rate of fuel burning of the vapor generator or by pressurization as set forth above. Retention time may be increased by the utilization of a second static steaming or conditioning vessel disposed in flow communication with the first that may also utilize the dynamic influx and counterflow of direct fired steam or merely provide a heat retention area for continued homogeneous conditioning of the ground full fat soy bean. In this manner, a marked advance over the prior art may be made by affording a product by process adapted for immediate consumption by livestock with maximum digestibility and nutrition.
The present invention creates a combination of conditions having specific ranges of temperature, moisture, acidity and oxygen. This resultant conditions eliminate trypsin inhibitors and urease, the two undesirable enzymes. Moreover, these conditions will also partially denature cellulose and protein contained in the endosperm around starch granules so that the starch granules can be exposed and made available to animals' digestive systems.
Surprisingly, the present invention produces a combination of temperature, pressure, moisture, acidity and low oxygen content that was found to be effective in denaturing or insolubilizing water soluble beta-glucans in barley. Although the precise mechanism is not known, the result was that barley feeds produced by the present invention had lower amount of water soluble beta-glucans and hence were less harmful to monogastric animals, such as chicken.
Although the presence of water soluble beta-glucans in barley may decrease the feed value of feeds for mono-gastric animals, the presence of these beta-glucans, however, may have hypocholesterolemic effects in several species, including man. Thus, it has been shown that chicks fed with barley containing beta-glucans have lower levels of low density lipoprotein cholesterol than the controls which were fed with either corn or barley having the beta-glucans removed or hydrolyzed. Concomitantly, chicks fed with barley containing beta-glucans have higher levels of high density lipoprotein cholesterol than those fed with either corn or barley containing low levels of beta-glucans.
Thus, depending on the intended use of the end product, the presence of beta-glucans in barley can be either desirable or undesirable. It would be advantageous, therefore, to have a conditioning system that, by altering one or various parameters, would condition the barley yet either would denature or insolubilize the beta-glucans or would leave most of the beta-glucans intact.
The present invention affords such a desirable capacity. Either singly or in combination, specific ranges of temperature, pressure, moisture, acidity and oxygen can be controlled and manipulated in the conditioning system. The resultant conditions can be manipulated toward the goal of either denaturing, insolubilizing or leaving intact beta-glucans in barley, depending whether or not the beta-glucans are needed in the end products.